Very few viruses are able to manifest as chronic infections or symptomatic acute infections in humans. Once intrinsic innate immune responses are ineffective at controlling virus replication, chronic viral infections are established or humans may die from a subsequent cytokine storm. In most organs, the first line of defense against invading viruses is the epithelial cell which provides initial immune response and subsequent immune control. Previous research on innate immune responses, specifically antiviral responses, have primarily focused on the characterization of pattern recognition receptors (PRRs), associated signaling molecules, and interferon (IFN) signaling pathways while also defining antiviral functions of interferon stimulated genes (ISGs). Recent studies of stem cell differentiation to hepatocytes have revealed differential regulation of ISG expression which contributes to host cell susceptibility to viral infection. Interestingly, epithelial cells predominantly produce type III interferons (IFNs) in response to viral infection whereas immune cells produce Type II IFNs (?) and Type I IFNs (?/?) are produced by most cells in the body. The mechanism underlying cell type and tissue specific expression of the type III IFNs are unknown and likely involve regulation of epigenetics modifications, gene expression of pattern recognition receptors and associated signaling molecules. We have developed novel and exciting in vitro models that utilize primary epithelial cells from several organs that have intact innate immune responses when compared to immortalized or transformed cell lines. We and others have shown that these cell types are of critical importance in the development of disease since they directly detect components of viral pathogens. We therefore assert that primary cells are the optimal model to use for studies on innate immunity and we propose a novel approach to study innate immunity based on the innate immune pathways that we have demonstrated to be important for microbial pathogenesis. In addition, we are developing novel physiologic models incorporating primary epithelial cells, stem cell-derived epithelial cells, 3-dimensional chip and microfluidic-based platforms. The use of stem cell-derived cells would facilitate the identification of changes in gene expression, which occur during differentiation, that contribute to the unique innate immune system in epithelial cells. The specific goal of this summer research supplement for David Barr is to support model development to further interrogate these organ specific host defense responses. Completion of these studies would offer the most in depth characterization of innate immunity in epithelial and other cell- types while improving our understanding of its contribution to human disease in multiple organs including those involving coronaviruses.